if statement == false

Comments

• juliebean@lemm.ee ⁨5⁩ ⁨months⁩ ago

  what would be the alternative? to always execute if the condition is true, but sometimes execute it even when false, for funsies?

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  • bstix@feddit.dk ⁨5⁩ ⁨months⁩ ago

    The “only” part implies exclusivity, which may be false, because other things might run the code anyway.

    IF “I can see the sun” THEN “It’s day.”

    Nothing wrong about that. However if we make it exclusive:

    IF AND ONLY IF “I can see the sun” THEN “It’s day.”

    That’s obviously wrong. I can actually not keep the day away by sitting with closed eyes in my mothers basement with the curtains shut.

    “Only if” might make sense in a legal contract, but there’s no way a piece of code can stop other pieces of code from calling the same functions.

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    • adj16@lemmy.world ⁨5⁩ ⁨months⁩ ago

      But that’s not how if statements in code work. So what you’ve said isn’t wrong, but the premise of this meme is completely off

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  • General_Effort@lemmy.world ⁨5⁩ ⁨months⁩ ago

    In normal parlance, “if and only if” rules out that something could also happen as a result of other circumstances. EG, if you fall out of a plane, you will lose your glasses. But there are other conditions that would lead to the same result.

    In code, the alternative would be to have a different if statement that executes identical code. Or *cough* ~you could use a jump statement to execute literally the same code.~

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  • unmagical@lemmy.ml ⁨5⁩ ⁨months⁩ ago

    Brb, making a truly “if” statement function in my products code base for funsies.

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• raoul@lemmy.sdf.org ⁨5⁩ ⁨months⁩ ago

  The boolean operator ‘If and only if’ do not have a relation with the program instruction ‘if’.

  The programatic ‘if’ is a jump, not a boolean operator. It do not have truth table.

  In logic:, if and iff can be seen like functions taking two booleans and returning a boolean

  • ‘if a then b’ (noted a -> b): return true if a is false or b is true. Example: ‘if I eat pizza then I fart’ This is true even if I fart all the time (if b is true, we do not care about the value of a) as long as I fart when eating pizza (if a is true, b must be also true)

  • ‘a <-> b’ is equivalent to ‘a -> b and b -> a’: the two should be true at the same time. I can only fart will eating pizza and cannot fart otherwise.

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  • Hoimo@ani.social ⁨5⁩ ⁨months⁩ ago

    So in programming, you’d write ‘if’ as:
    not pizza or fart where the farting is irrelevant until the pizza is involved.

    While ‘iff’ would be:
    pizza equals fart where pizza means fart and no pizza means no fart.

    I actually wrote iff as (not pizza and not fart) or (pizza and fart) before, and I’m pretty sure that’s the way I wrote an iff in production code in the past, but your comment made me realize that “they should be true at the same time” can be tested really easily with equality.

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    • Venator@lemmy.nz ⁨5⁩ ⁨months⁩ ago

      I don’t love the pizza fart variable naming convention, but it’s better than foobar and I don’t have a better suggestion 😅

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    • captain_aggravated@sh.itjust.works ⁨5⁩ ⁨months⁩ ago

      If not pizza and not fart: pass

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• stevedice@sh.itjust.works ⁨5⁩ ⁨months⁩ ago

  No, they’re not.

  Let’s assume they are. Let funky function be defined as:

  int funky() {
      a=0
      b=1
      if ( a==1 ) {
          b=1
      }
      return(a)
  }
  

  Since a==1 if, and only if b=1, in particular a==1 if b=1. We have b=1, therefore a==1. It follows funky will always return 1 but… it doesn’t. QED.

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  • nickwitha_k@lemmy.sdf.org ⁨5⁩ ⁨months⁩ ago

    I’m pretty sure that funky() would always return 0, as defined. I’ll pseudocide that up:

    funky takes no args, returns int {
      a is assigned the value 0
      b is assigned the value 1
    
      test if a is equal to 1, if it is {
        b is assigned the value 1
      }
    
      return a
    }
    

    The if in your function can never be reached, without some weird manipulation of the value of a that breaks variable scoping in most syntaxes.

    I think that I see your logic but it is syntactically incorrect:

            b=1
        }
    

    In most syntaxes, this is a conditional execution and value assignment. That is, the code in curly braces only gets executed, if the conditional evaluates as true. If the conditional evaluates as true, the code is executed, assigning the value 1 to the variable b.

    It does NOT imply that the assignment of the value 1 to the variable b is a conditional requiring the assignment of the value 1 to the variable b.

    Remember: = in most programming is NOT an equality symbol but a value-assigment symbol. It would be nice if people creating the initial syntaxes used something else that is harder to confuse but they didn’t.

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    • ikilledlaurapalmer@lemmy.world ⁨5⁩ ⁨months⁩ ago

      Yeah, I’m not sure what the original intent was here. If we’re missing something I’d like to know

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    • stevedice@sh.itjust.works ⁨5⁩ ⁨months⁩ ago

      Yes, I know, that’s the point. Funky is specifically constructed to always return 0. Then we assume “if” and “if, and only if” are equivalent and by following that assumption of its logical conclusion, we deduce that funky returns 1. Therefore, our assumption was incorrect because 0≠1. It follows that “if” isn’t equivalent to “if, and only if”. Also, it’s just a shitpost.

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  • ninja@lemmy.world ⁨5⁩ ⁨months⁩ ago

    Translating structured logic into spoken language is iffy. (I’m sorry. I couldn’t help myself)

    The code reads to match OP if stated as: “If and only if the value of ‘a’ equals 1 then set the value of ‘b’ to equal one.” Placing the conditional at the beginning of the sentence maintains the correct dependency.

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    • stevedice@sh.itjust.works ⁨5⁩ ⁨months⁩ ago

      I agree but it’s also what the original meme is doing. I thought we were all shitposting here.

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• sik0fewl@lemmy.ca ⁨5⁩ ⁨months⁩ ago

  I hope this memer is not a programmer or logician, but ideally neither.

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• eunieisthebus@feddit.org ⁨5⁩ ⁨months⁩ ago

  Waiting for a programming language with iff Syntax

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• dohpaz42@lemmy.world ⁨5⁩ ⁨months⁩ ago

  An if statement with one condition is an if and only if statement. The moment you add a second (or more) condition (regardless of && or ||), then it’s no longer if and only if.

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• Hammocks4All@lemmy.ml ⁨5⁩ ⁨months⁩ ago

  If and only if… haha unless…

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• reallykindasorta@slrpnk.net ⁨5⁩ ⁨months⁩ ago

  IFF you use the universal quantifier

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• BreadOven@lemmy.world ⁨5⁩ ⁨months⁩ ago

  Don’t you just use iif?

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• GammaGames@beehaw.org ⁨5⁩ ⁨months⁩ ago

  Reminds me of this fun stack exchange q

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